Cloned Pigs Produce Healthy Pork?

Amitabh Avasthi
for National Geographic News
March 27, 2006
Pigs have been genetically modified to make their meat as healthy as seafood, researchers report.

But concerns over food safety and the U.S. federal approval process may prevent the tricked-up pork from appearing in supermarkets anytime soon.

The premise of the work, published yesterday in the online journal Nature Biotechnology, is based on cloning pigs to genetically express higher levels of omega-3 fatty acids, a type of natural oil that is thought to fight heart disease and various immune disorders. The oils are typically found in fish.

"Omega-3 fatty acids are crucial to human health," said Jing Kang, associate professor of medicine at Harvard Medical School in Cambridge, Massachusetts.

"But the source is increasingly limited, due to declining fish stocks and contamination from mercury and other harmful chemicals. We need a cheap, land-based alternative to meet the growing demand, and these pigs could be the answer."

Cloning for Healthy Pork

Until now the only way to enrich livestock with these fatty acids was to supplement their feed with expensive fish meal, Kang explains. That's because the animals lack a specific gene that helps convert less healthy omega-6 fatty acids into their healthier omega-3 form.

During experiments in 2004, Kang and his colleagues transplanted that gene into mice to create mice that could produce the omega-3 fatty acids.

For their work on pigs, the researchers introduced a similar version of the gene—tweaked for use in pigs—into the fetal cells of male pigs and singled out those cells that produced higher amounts of omega-3.

The researchers then implanted material from those altered cells into unfertilized pig eggs and transplanted the embryos grown from the eggs into 14 sows.

Of the ten live piglets born from the pregnancies, six tested positive for the gene that produces omega-3 fatty acids.

"Tissue samples from the tails of the transgenic pigs indicated higher levels of omega-3 fatty acids and lower levels of omega-6 fatty acids," Kang said.

Kang says he plans to replicate the work in cows and chickens.

Approval and Apprehension

Experts say it may be a while, if at all, before pork that is as healthy as salmon appears in supermarkets.

In the United States all genetically modified animals have to be approved by the U.S. Food and Drug Administration (FDA) before they can be sold commercially.

To date the FDA has not permitted the sale of any such animals for food. An application seeking approval of genetically engineered fish has been pending for nearly six years.

"It is too early for the FDA to have received an application from the researchers seeking approval," a spokesperson for the agency said of Kang's pigs.

Kang's research has prompted concerns from some experts about food safety and animal welfare, while others have questioned the secretive nature of the approval process.

(See a National Geographic magazine feature about the benefits and risks of genetically modified foods.)

"The application process is confidential, and the FDA needs to have a transparent process that addresses the public's moral and ethical concerns towards animal cloning," said Michael Fernandez, executive director of the Pew Initiative on Food and Biotechnology in Washington, D.C.

According to Margaret Mellon, who heads the Food and Environment Program at the Boston-based nonprofit Union of Concerned Scientists, Kang's work "raises serious questions about interfering with fatty acid metabolism."

"We don't know about the fat levels in adults and in future generations. There has been no study on the effect it might have," Mellon said.

Responding to Kang's point about declining fish stocks, Mellon added, "We need to solve the ocean crisis and not push it as an excuse for introducing genetically modified food."

Opinion on the benefits of omega-3 fatty acids is mixed as well.

A study published online this week in the British Medical Journal suggests that evidence of potential health benefits from the fatty acids may be less conclusive that had been thought.

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